Eating disorders (EDs) are complex conditions with one of the highest mortality rates among psychiatric illnesses. While outpatient evidence-based treatments for EDs in adults exist, there is often utilisation of more intensive interventions as part of treatment. However, a comprehensive analysis of the impacts of intensive treatment (inpatient, residential and day program) on physical and psychosocial outcomes is lacking. Thus, the current systematic review and meta-analysis aimed to investigate the effectiveness of intensive treatments in adults with EDs for the outcomes of body mass index (BMI), disordered eating, depression, and quality of life, as well as a moderation analysis investigating a range of clinical characteristics. Overall, 62 studies were included in the meta-analysis. The results revealed that intensive treatment in adults yielded significant improvements in BMI (for underweight patients), disordered eating, depression, and quality of life. Treatment setting, length of stay and geographical region of the study all served as moderators for disordered eating and depression. Nevertheless, given the high heterogeneity in the meta- and moderation analyses, these results should be interpreted with caution. Future high-quality research is needed to determine the most beneficial elements of intensive treatment (compared to outpatient) in adults with EDs.